• Journal of the Mineralogical Society of Korea
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• v.26 no.2
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• pp.111-118
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• 2013

Diagenetic black chert nodules occur in the Paleozoic dolostone in Susan, Jecheon, Korea. They reacted with dolomite to form alteration rim around the nodules during the contact metamorphism probably related to the intrusion of biotite granite. In the earlier stage of alteration, talc and calcite replaced both the chert and dolomite, which were subsequently replaced by tremolite. Significant mass of tremolite occurs along the horizon enriched with chert nodules. Scanning electron microscopy and optical microscopy of the tremolite specimens revealed the elongated morphology of diverse aspect ratios coexisting in several mm scale. Non-asbestiform tremolite columns were also common as well as asbestiform fibrous bundles. Quantitative estimation of asbestos should be more cautious for naturally occurring materials because all the tremolite particles in the outcrop are not asbestiform. The occurrence of asbestiform tremolite in the Susan area indicates that a combination of chert-bearing dolostone, heat source, and aqueous fluids is one of the geological environments for the formation of asbestiform tremolite.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.3
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• pp.69-74
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• 2009

A novel protocol is proposed to achieve sub-carner-based rate adaptation in OFDM-based wireless systems. The protocol requires the addition of one OFDM symbol to the Clear-to-Send (CTS) packet defined in the IEEE 802.11 standard_ When receiving a Ready-To-Send (RTS) packet, the receiver determines the number of bits to be allocated in each sub-carrier through channel estimation. This decision is delivered to the sender using an additional OFDM symbol. That is, bit-allocation over sub-carriers is achieved using only one additional OFDM symbol. The protocol also provides an error recovery process to synchronize the bit-allocation information between the sender and receiver. The protocol enhances the channel efficiency in spite of the overhead of one additional OFDM symbol.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.10 no.1
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• pp.15-22
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• 2012

Purpose : We investigated the effects of the combined use of FES and over ground walking with partial body-weight support (PBWS) on walking function and balance control in people with chronic strokes. Methods : Twenty-seven people who were ambulatory after chronic strokes were evaluated. The exercise's intervention consisted of the combined use of FES and over ground walking with PBWS and general exercise groups. The FES + PBWS group and general exercise group consisted on a-20-minute session per day, 3 times a week during a 4 week period. The evaluation was carried out before, after, and two weeks after the exercise intervention. Outcome measures were a 6 Minute Walk Test, 6-Meter walk Test, Timed Up and Go Test, and a Balance Test, measured before and after the exercise interventions at a-2 week follow up. Results : The endurance was significantly increased in both the FES+PBWS group and general exercise group (p<0.05). Significant increase on the gait velocity was observed in both the FES+PBWS group and general exercise group (p<0.05). The TUG was significantly different in both the FES + PBWS group and general exercise group (p<0.05). However there were no differences in both the between-group & interaction. The stability index was significantly different in both the FES + PBWS group and general exercise group (p<0.05). Conclusion : In conclusion, the combined use of FES and over ground walking with PBWS led to an improvement in walking function and balance control. Thus, it is possible to combine the use of FES and over ground walking with PBWS for physical therapy intervention to improve walking function and balance control. It is suggested to apply this intervention in the clinical field.

• Journal of the Korean Academy of Clinical Electrophysiology
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• v.8 no.2
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• pp.13-18
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• 2010

Purpose : This study investigates the effects on balanced ability and ankle joint muscle following balance pad and trampoline training periods in order to report a clinical directing about this matter. Methods : A total of nine members participated in a balance training program that put a balance pad and trampoline to use. Participants trained three times a week for thirty minutes in groups of six. Resting time was set for two minutes. EMG (median frequency and root mean square) was used to measure muscle activity at 3 weeks and 6 weeks, respectively. The tibialis anterior and gastrocnemius muscles were measured. Participants were measured with eyes open and closed. Results : The median frequency showed a significant difference according to the change in time in both muscles. Also, results showed a significant interaction between eyes open and closed in the gastrocnemius muscle. The root mean square only showed a significant difference according to the change in time in the gastrocnemius muscle. Conclusion : We suggest that the balance pad and trampoline training influence a decrease in the recruitment rate of slow twitch muscles through an improvement in balance ability; however, the training did not show a statistically significant difference with regards to eyes open and closed.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.40 no.5
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• pp.312-320
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• 2003

This work describes an 8b 200 MHz 0.18 urn CMOS analog-to-digital converter (ADC) based on a pipelined architecture for flat panel display applications. The proposed ABC employs an improved bootstrapping technique to obtain wider input bandwidth than the sampling tate of 200 MHz. The bootstrapuing technique improves the accuracy of the input sample-and-hold amplifier (SHA) and the fast fourier transform (FFT) analysis of the SHA outputs shows the 7.2 effective number of bits with an input sinusoidal wave frequency of 500 MHz and the sampling clock of 200 MHz at a 1.7 V supply voltage. Merged-capacitor switching (MCS) technique increases the sampling rate of the ADC by reducing the number of capacitors required in conventional ADC's by 50 % and minimizes chip area simultaneously. The simulated ADC in a 0.18 um n-well single-poly quad-metal CMOS technology shows an 8b resolution and a 73 mW power dissipation at a 200 MHz sampling clock and a 1.7 V supply voltage.

• Journal of the Korean Society for Railway
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• v.20 no.4
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• pp.466-473
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• 2017

Recently, domestic railway related institutes are developing pantographs for high speed trains; to lighten the upper arm, this device has a composite structure of CFRP (Carbon Fiber Reinforced Plastic) and aluminum instead of conventional steel. In the case of KTX-Sancheon, the pantograph must have a large current capacity because this system is of power-car type, supplying all necessary power for the train through a single pantograph. If the thickness of the pipe is arbitrarily increased in order to increase the current carrying capacity, without analyzing the thermal characteristics of the aluminum pipe, the increase in the weight of the upper arm may cause degradation of the current collecting performance. Therefore, in this paper, using the thermal analysis technique, we analyze the temperature change characteristics of the aluminum pipe of the upper arm over time, while receiving power at the stationary state of the KTX-Sancheon; we also examine the adequacy of the minimum thickness of the aluminum pipe in accordance with the proposed pantograph flow capacity.

• The Korean Journal of Financial Management
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• v.22 no.1
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• pp.37-69
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• 2005

This study intends to verify whether stock repurchase, as well as stock dispositions, affects shareholder's wealth and also whether repurchase/dispositions has varying impact de-pending on its purpose. According to empirical analysis, announcement of stock repurchase results in positive abnormal returns when the objective of stock repurchase is stock price stabilization or cancellation of shares. However, when the purpose of stock repurchase is granting incentives to executives/employees, we get the negative abnormal returns. Also, the termination of stock trust for reason of expiration or stock dispositions of which goal is to give incentives to executive/employees has a negative impact on stock price, whereas direct dispositions of stock to raise cash or to improve financial structrue are shown to significantly increase the wealth of shareholders. Cross-section analysis also confirms that stock repurchase and dispositions has different impact on excess returns depending on its purpose. The results of this study imply that the dispositions of stock should be regarded as an important financial strategic tool to be used by companies and what's more, such studies dealing with stock repurchase or dispositions should take firm's purpose into consideration in their approach.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.19 no.3
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• pp.287-299
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• 1997

Procurement, cutting, cleansing, freezing, freeze-drying, and demineralization of the allogeneic bone must be made under the germ-free stable condition without bacterial and/or viral contamination. Even thought the bone is procured under the germ free condition, we must have confidence on disinfection of all the solutions that come in contact with tissue during the whole procedure. Lots of antibacterial agents have been introduced for chemical sterilization. Recently ethylene oxide gas sterilization or radiation sterilization is frequently selected as a secendary sterilization procedure. The biological and biochemical response of the graft material differs with the type and concentration of the sterilizing agents, and various toxic reactions have been reported due to the graft material itself and the substance released by the chemicals. The authors conducted the Millipore filter test to observe the toxic effect on L929 fibroblasts according to the effect on activity of succinate dehydrogenase, during the secondary sterilization of the demineralized allogeneic bone powder with irradiation or ethylene oxide gas. The result were as follows : 1. Around the copper disk, positive control group, 10mm diameter discoloration was observed. 2. As same as the negative control group, the disk showed no discoloration. 3. The demineralized allogeneic bone which was sterilized with ethylene oxide gas or irradiation showed no cytotoxicity. 4. From this results, it is suggested that treatment with ethylene oxide gas or irradiation should be effective to sterilize the deminineralized allogeneic bone.

• Journal of Navigation and Port Research
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• v.36 no.5
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• pp.349-355
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• 2012

In this study, for the purpose of reduction of $CO_2$ gas emission and to increase recovery of waste heat from ships, the ORC(Organic Rankine Cycle) is investigated and offered for the conversion of temperature heat to electricity from waste heat energy from ships. Simulation is performed with waste heat from the exhaust gasse which is relatively high temperature and cooling sea water which is relatively low temperature from ships. The result shows that 1,000kW power generation is available from exhaust gas and 600kW power generation is available from sea water cooling system. Different fluid is used for simulation of the ORC system with variable temperature and flow condition and efficiency of system and output power is compared.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.05a
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• pp.291-294
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• 1999

The effect of AI$_2$O$_3$+Y$_2$O$_3$additives on fracture toughness of $\beta$-SiC-ZrB$_2$composites by hot-pressed sintering were Investigated. The $\beta$-SiC-ZrB$_2$ ceramic composites were hot-presse sintered and annealed by adding 1, 2, 3wt% AI$_2$O$_3$+Y$_2$O$_3$(6:4wt%) powder as a liquid forming additives at 195$0^{\circ}C$ for 4h. In this microstructures, no reactions were observed between $\beta$-SiC and ZrB$_2$, and the relative density Is over 90.79% of the theoretical density and the porosity decreased with increasing AI$_2$O$_3$+Y$_2$O$_3$ contents. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed the highest of 5.5328MPa . m$^{1}$2/ for composites added with 2wt% AI$_2$O$_3$+Y$_2$O$_3$ additives at room temperature. But the standard deviation of fracture toughness of specimens decreased with increasing AI$_2$O$_3$+Y$_2$O$_3$ contents and showed the highest of 0.8624 for composite tilth 1wt%, AI$_2$O$_3$+Y$_2$O$_3$additives.